Electric fuse



Nov. 8, 1960 W, A. GASKILL ETAL ELECTRIC FUSE Filed March 2, 1959INVENTOR. FIG. 3 W/LL/AM A GASK/LL W/LL/AM H RU SELL va/; W

ATTOR NEY United States Patent ELECTRIC FUSE William A. Gaskill,Hampton, and William H. Russell,

Forest Park, Ga., assignors to Southern States Equipment Corporation, acorporation of Georgia Filed Mar. 2, 1959, Ser. No. 796,599

3 Claims. (Cl. 200--127) This invention relates to electric fuses andmore particularly to electric fuses which are especially adapted tointerrupt a wide range of fault currents.

In electric fuses of the type in which an outer shell houses a fusibleelement it has been the practice to arrange a biasing means to reactagainst the shell and against one end of the fusible element in such away as to aid in ejecting the one end of the fusible element uponrupture of the fusible element during a circuit interrupting operation.Such fuse ejecting operations facilitate interruption and, in addition,serve as insurance against the retention of both ends of the fusibleelement within the housing structure immediately following a circuitinterrupting operation. By ejecting one end of the fusible element aftercircuit interruption the possibility of having the circuit reestablishedis minimized or eliminated. The structure using the biasing means abovedescribed sometimes fails to interrupt the circuit during low currentconditions due to the fact that low currents generate very low pressuresresulting in poor scavenging of the fuse housing structure.

A principal object of this invention is the provision of an improvedfuse structure wherein means are provided for promptly and quicklyejecting one end of a fusible element from within its fuse tube andwherein means are provided for facilitating interruption during lowfault conditions.

Still another object of the invention is the provision of an improvedhigh voltage electric fuse wherein means are provided for facilitatinginterruption during low faults and which'means also operates promptly toeject one end of the fusible element from the fuse tube after theperformance of a circuit interrupting operation.

The invention in one form as applied to an electric fuse comprises afuse tube, a fusible element mounted within the fuse tube and having oneend of the fusible element secured within the fuse tube, a closureelement disposed adjacent one end of the fuse tube and arranged normallyto constitute closure means therefor, and a releasable biasing elementoperably related with the free end of the fusible element and with theclosure element, the releasable means being effective to hold theclosure element in its tube closing position for a short time aftercircuit interruption and which is operable shortly thereafter to aid inejecting the free end of the fusible element from within the fuse tube.

The invention will be better understood from the following detaileddescription taken in conjunction with the accompanying drawings in whichFig. 1 is a side view of a conventional power fuse to which theinvention is applied; Fig. 2 is an enlarged view partially in section ofthe lower end of the fuse tube and its mounting structure shown in Fig.1 but with certain elements removed for 2,959,652 Patented Nov. 8, 1960ICC clarity; Fig. 3 is an enlarged cut-away view partially in section ofthe lower end of a fuse tube to which the invention has been applied andwhich shows the essential features thereof in their normal closedcircuit positions before the beginning of an interrupting operation; andin which Fig. 4 is a view similar to Fig. 3 but which shows the parts inthe positions which they occupy during the performance of a circuitinterrupting operation.

With reference to Fig. l, the numeral 1 denotes a base structure such asa metallic channel member adapted to be mounted on suitable supportingstructure. AffiXed to the upper end of channel support 1 is an insulatorstack 2 while a similar insulator stack 3 is affixed in known fashion tothe lower end of channel 1. Secured to the right-hand end of insulatorstack 2 is a terminal element 4. Terminal element 4 is mounted toinsulator stack 2 by means of a plurality of bolts 5 and a terminal pad6 by which connection is made to the circuit controlled by the fuse isintegrally formed with terminal structure 4. Pivotally mounted to theright-hand end of terminal element 4 is a sleet hood 7, the pivotalconnection between hood 7 and terminal element 4 being by way of thepivot pin 8. As is well understood in the art, the sleet hood 7 isprovided on the interior surface thereof with a latching surface notshown in the drawings. This latching surface formed within the sleethood 7 engages the left-hand extremity of terminal structure 9 securedby a pressed fit and by means of pin 10 to the upper end of fuse tube11. As is wellunderstood in the art, the terminal element 9 may beprovided with a ring structure 12 through which the end of a hookstickmay be inserted for operation and handling of the fuse. Furthermore, ifdesired, the upper end of the fuse tube 11 may be provided with areleasable closure element generally designated in Fig. l by the numeral13. If desired, this releasable closure element 13 could be constructedin accordance with the disclosure of patent application Serial Number663,479, filed June 4, 1957, by Olan Richardson which issued as Patent2,903,538 and which is assigned to the assignee of this invention.

Secured to the lower end of the fuse tube 11 is terminal structuregenerally designated by the numeral 14. This terminal structure 14 issecured to the fuse tube 11 by a pressed fit and by a suitable fasteningpin such as is designated by the numeral 14A in Fig. 3.

As is shown in Fig. l, the lower end of the fuse tube 11 and itsassociated terminal structure 1.4 is mounted on the terminal element 15secured by a plurality of bolts 16 to the right-hand end of theinsulator stack 3. Formed integrally with the terminal element 15 is aterminal pad 17 by which connection is made in known manner to thecircuit controlled by the fuse tube. If desired, the fuse shown in Fig.1 may be provided with a buffer device 13 which is mounted in knownfashion on the terminal element 15 and which acts to arrest the downwardswinging movement of the fuse holder 11 and parts associated therewithduring a circuit interrupting operation.

As is best shown in Fig. 2, a conducting element 19 is connected by apivot pin 20 to the terminal element 14. Furthermore, as is shown inFig. 2, the conducting element 19 is provided with a pair of trunnions21 which engage a pair of spaced jaws 15A constituting essentialelements of the terminal element 15.

As is well understood in the art, the conducting element 19 is held inthe position shown in Fig. 2 by means of the fuse link 22 which issecured by bolt 23 to the conducting element 19, the other end offusible element 22 being in contact with terminal structure 9 as is wellknown. Thus so long as the fusible element 22 disposed within the fusetube 11 is intact the conducting element 19 is held in the positionindicated in Fig. 2.

The circuit between terminal element 15 and conducting element 1.9 ismaintained by conducting brush 24 which is secured to terminal element15 by the bolt 25 and which engages the surface 14A of conductingelement 19.

When the fusible element 22 ruptures duringa circuit opening operationthe conducting element 19 swings in a clockwise direction about thetrunnions 21 and the lower end of the fuse tube 11 moves downwardly andsomewhat to the right as swinging movement about pin 20 occurs. Shortlythereafter the latch at the upper end of the fuse tube between theterminal structure 9 and the sleet hood 7 is released and the entireassembly associated with the fuse tube 11 swings clockwise about thetrunnions 21 to establish a circuit interrupting gap between terminals 6and 17.

As is well known, the fuse tube 11 constitutes an outer shell ofinsulating material 11A and an inner fiber liner 11B. i i

In accordance with a feature of the invention the lower end of the fusetube 11 may be counterbored as is indicated by the numeral 26. Securedwithin the counterbored portion 26 of the fuse tube is a disc-shapedclosure means 27 which is freely slidable on the fusible element 22 dueto the fact that the disc 27 is provided with a centrally disposedopening through which the fusible element 22 extends and which is largerthan the fuse link. Disposed to engage the lower surface of the closureele ment 27 is a compression spring 28 the lower end of which engagesthe flange 29 of a ferrule 30 which is secured to the fuse link 22 byindenture means designated at 31 or by other suitable known means.

Thus as is shown in Fig. 3, the closure element 27 is biased upwardlyagainst the shoulder 26A by the helical spring 2% the lower end of whichis held in position by the fiange 2% of the ferrule 30.

it will be understood that when the fuse link 22 is ruptured due toover-current conditions for example, the helical spring 23 promptlyexpands causing the ferrule 29 and the lower end of the fusible element22 to be drawn downwardly to the positions of the parts as indicated inFig. 4. During this initial portion of a circuit interrupting operationthe closure element 27 is maintained securely in its tube closingposition against the counterbored shoulder 26A. Thus if the interruptingcurrent is of a low order of magnitude the tubewill remain closed and,for at least a short time, sufiicient pressure will be developed withinthe interior of the fuse tube 11 to aid substantially in interruptingsuch low fault currents. In this way interruption of low currents ismaterially facilitated according to a feature of the invention. A

After interruption, spring 28 acts as an ejecting means thereby quicklyto withdraw the entire lower end of the fusible element 22 and to ejectit from the lower end of the fuse tube 11. Of course the closure element27 ordinarily is blown out of the lower end of the fuse tube by thepressure generated by the are being interrupted.

In the case of high voltage fuses the fusible element .22 is quite longand may tend to clog up the lower end of the fuse tube and thereby tointerfere with efiicient ejection of the lower end of the fusibleelement 22. In this connection, and according to a feature of thisinvention, the biasing element 28 aids considerably in ejecting thelower end of the fusible element by exerting a downward pull thereonthereby effectively to prevent wadding of the fusible element withinthelower portion of the fuse tube 11.

Should the fuse be called upon to interrupt high current arcs, ejectionof the lower end of the fusible element 22 is facilitated. When 'a highcurrent are is .formed within the fuse tube :a large pressure is quick-1y generated and bears against the upper surface of the closure element27. Such pressure may cause the closure element 27 to move downwardquickly but in such event this downward movement tends to compress thehelix 28 thereby aiding in ejecting the lower end of the fusible element22.

While we have shown and described a particular embodiment of theinvention we do not wish to be limited thereto and intend in theappended claims to cover all such changes and modifications as fallwithin the true spirit and scope of the invention.

What we claim as new and desire to secure by Letters Patent of theUnited States is:

1. A high voltage electric fuse comprising a fuse tube of insulatingmaterial having fault responsive gas emitting material along at least apart of its inner surface, a fusible element disposed within said tube,said fusible element having one end thereof secured within said tube andhaving the other end thereof extending toward an end of said tube, saidfusible element being flexible and being of such size as to occupy asubstantial part of the space within said tube and having a tendency toclog in said tube during low current faults, closure means normallyclosing the said end of said tube, and yieldable biasing means normallyreacting between said fusible element and said closure means and.normally effective to maintain said closure means in its tube closingposition, said biasing means being interrelated with said fusibleelement and closure means so as to aid in ejecting said other end ofsaid fusible element from said tube in coordination with the performanceof a circuit interrupting operation by said fusible element and beingeffective to react against said fusible element during low currentfaults so as to maintain said tube in sealed condition for a briefperiod following rupture of said fusible element to allow an effectiveare quenching pressure to build up in said tube.

2. An electric fuse comprising a fuse tube of gas emitting insulatingmaterial, said tube being counterbored at one end, a fusible elementdisposed within said tube, said fusible element having one end thereofsecured within said tube and having the other end thereof extendingtoward said one end'of said tube, said fusible element also beingflexible and having a tendency to clog in said tube particularly duringlow current faults, closure means disposed within the counterbored endof said fuse tube and normally closing'the said end of said tube, andbiasing means normally reacting between said fusible element and saidclosure means and normally effective. to maintain said closure means inits tube closing position, said biasing means being positioned relativeto said fusible element and to said closure means so as to aid inejecting said other end of said fusible element from said tube incoordination with the performance of a circuit interrupting operation bysaid fusible element and being effective to react against said fusibleelement during low current faults so as to maintain said tube in sealedcondition for a brief period following rupture of said fusible elementto allow an effective arc quenching pressure to build up in said tube.

3. Anelectric fuse comprising a fuse tube of insulating material, saidtube being counterbored at one end, a fusible element disposed withinsaid tube, said fusible element having one end thereof secured withinsaid tube and having the other end thereof extending toward said one endof said tube, said fusible elementbeing flexible and of such size as tooccupy a substantial part of the space within said tube, closure meansdisposed within-the counterbored end of said fuse tube and normallyclosing the said end of said tube, said closure means being disc shapedand having an opening therethrough through which the said other end ofsaid fusible element extends in slidable relation, and low inertiareleasable means arranged normally to engage said closure means andeffectjiye normally to hold said closure means inits tube closingposition, said releasable means being operable References Cited in thefile of this patent upon rupture of said fusible e1ement to release saidUNITED STATES PATENTS I closure means from 1ts normal tube closingposition only after a brief time delay period following rupture of said2043O24 Wflhams June 1936 fusible element upon the occurrence of a lowfault cur- 5 2450102 f 1939 rent condition and being effective promptlyto release 22081440 Wlulams Juy 1940 said closure means from its tubeclosing position upon 2281795 Plttman et a 1942 the occurrence of a highfault current condition and said gg' r zz g releasable means beingeffective to aid in ejecting said other end of said fusible elementfollowing interruption. 10

